1. Field of the Invention
The present invention relates to a data communication method in a mobile communication system, and in particular, to a method for reducing battery power consumption of a mobile station when no user traffic is transmitted thereby, while maintaining a dedicated control channel.
2. Description of the Related Art
At present, mobile communication systems using a Code Division Multiple Access (CDMA) protocol operate in accordance with the IS-95 standard, which supports voice service only. In the near future, mobile communications will be performed according to an International Mobile Telecommunication-2000 (IMT-2000) standard which supports high speed packet data service as well as voice service. The IMT-2000 Standard aims at multimedia services such as high quality voice service, a moving picture service, an Internet search service, etc.
A mobile communication system with packet data communication capability transmits data in bursts, with relatively long and frequent standstill periods between bursts in which data is not transmitted, in accordance with the packet data traffic pattern. Hence, for future mobile communication systems, there has been proposed a technique for xe2x80x9cconnectingxe2x80x9d data communication channels only when the data bursts are transmitted during the packet data communication. xe2x80x9cConnectingxe2x80x9d channels refers to the process of becoming properly set up on both sides of the radio link to enable immediate communication. Taking into consideration the limited radio resources, the base station air capacity and the battery power of the mobile terminal, it is desirable to connect a dedicated traffic channel only while the data is transmitted; to release the traffic channels for other mobile stations while the data is not transmitted; and quickly re-connect the channels when user data appears.
However, to reassign the traffic channel and the control channel in order to re-start transmitting the data after stoppage of the data transmission, channel renegotiation is generally necessary between the base station and the terminal. This re-negotiation procedure may result in additional signaling overhead and latency. The signaling overhead includes a control message necessary for synchronization of a radio link protocol (RLP), and a control message necessary for the service negotiation made during the re-connection of the data service.
A number of data communication methods have been proposed for use in mobile communication systems. For example, U.S. Pat. No. 5,673,259 discloses a random access communication channel for data services suited for use in CDMA applications. In that patent, mobile terminals transmit data packets on the random access channel on a reverse link to a base station. When bandwidth demand exceeds a first threshold, a processor switches from the random access channel to a dedicated channel for communicating the data packet between the mobile terminal and the base station. When the bandwidth drops below a second threshold, the processor switches from the dedicated channel to the random access channel.
Another example is International patent application WO95/35637 (U.S. Pat. No. 5,754,541) which discloses a data transmission method in a CDMA cellular radio network. Signals transmitted by mobile stations are divided into bursts in the time domain. The system therein strives to achieve high traffic capacity by means of a base station transmitting information to mobile stations about the load state of a traffic channel used by the base station. The number of bursts transmitted between the mobile stations and the base station per time unit is controlled on the basis of the delay state of the bursts and the load state information computed at the base station.
It is an object of the present invention to provide a method for increasing utilization efficiency of channel resources by connecting and releasing channels in accordance with the presence/absence of traffic data transmitted during a packet data communication in a mobile communication system.
It is another object of the present invention to provide a method for increasing channel efficiency and conserving mobile terminal transmission power by controlling outputs of a dedicated control channel and a pilot channel when data transmission is discontinued temporarily during the data communication in a mobile communication system.
According to one aspect of the present invention, a data communication method is provided in a base station of a mobile communication system including an active state in which user data is transmitted through a dedicated traffic channel and control messages are transmitted through a dedicated control channel. In accordance with this method, a transition is made from the active state to a first control hold state when there is no data to transmit for a first set time. In the first control hold state, the dedicated traffic channel is released while the dedicated control channel is maintained. A transition is made from the first control state to a second control hold state when there is no user or control data to transmit for a second set time. In the second control hold state, the transmission output of the dedicated control channel is interrupted.
According to another aspect of the present invention, a data communication method is provided in a terminal of a mobile communication system, in which a pilot signal is transmitted by the terminal through a reverse pilot channel. A transition is made from an active state to a first control hold state which releases a dedicated traffic channel and maintains a dedicated control channel and the reverse pilot channel. Another transition is made from the first control hold state to a second control hold state where the transmission outputs of a dedicated control channel and reverse pilot channel are controlled to conserve power.